Fluid flow around an object such as an airplane wing generates aerodynamic forces, including lift and drag. A thick boundary layer and flow separation from a surface of the object adversely affects the aerodynamic performance. Vortex generators (VGs) have been used in passive flow control applications such as on wings at transonic speeds to generate vorticity, or more circulation of the airflow in the boundary layer, thereby delaying or eliminating flow separation. Streamwise vorticity inside the boundary layer is desirable, which improves the aerodynamic performance of the object.
Typical vortex generators generally have a height close to the boundary layer thickness and thus generate undesirable parasitic drag. “Low-profile” or micro-VGs (μVGs) have been proposed to reduce the parasitic drag while producing benefits similar to those of traditional VGs. The micro-VGs generally have a height less than the boundary layer thickness.
When air flows at supersonic speeds, such as at supersonic inlets, a shock wave is generated. Shock wave interaction with a turbulent boundary layer has an adverse impact on the aerodynamic performance of the supersonic inlets, such as shock-induced flow separation, increased thickness in boundary layer, and stagnation pressure loss.
A typical flow control method is to bleed the flow at the shock impingement to suppress separations, which thins the boundary layer and increases the pressure recovery. However, bleeding the flow has a significant penalty cost of removing up to tenth of the incoming mass flow in order to function effectively. This requires larger inlets to compensate for the lost mass flow which can lead to weight increase and drag. Therefore, improved flow control devices that can reduce or completely eliminate bleeding are desirable.